Since the advent of firearms and the like, superior shooting skills have been a key factor in the effective use of these devices. Such shooting skills usually combine visual acuity with dexterous handling of the firearm to accurately aim the firearm at a target. Accurate shooting is a process that usually starts with visual acquisition of a target. The process continues by aiming of a firearm at the target, often with a sighting device. Once the firearm is aimed at a target and a decision made to fire a projectile at the target, the firearm is actuated so that a projectile is released from the firearm at the target. In situations involving a moving target, accurate aiming of a firearm at the target requires a concerted effort to continuously adjust the firearm user's visual perception of the target while performing physical adjustments of the firearm to keep the firearm accurately aimed at the target.
Most firearms and other projectile propulsion devices are similar in that they enable a vectored propulsion force to be applied to a projectile in order to propel the projectile a distance in substantially the same direction as the applied vectored force. A variety of sighting devices have been developed to aid a shooter in making aiming adjustments of the firearm at a target. Generally speaking, there are two types of conventional sighting devices used with projectile propulsion devices. The first type is commonly known as a notch sight. The second type of sight is referred to as an aperture sight.
A notch sight is usually made of solid material with a notch, or three sided cut-out, centrally placed in the material such that a field of view can be seen through the notched portion of the sight when aiming a firearm with the sight. Most notch sights are placed on a rear portion of a firearm. These rear notch sights are most often used in combination with a vertical front sight placed near the front, or open end, of the firearm's barrel. Most vertical front sights take the form of a blade or a post. In use, the vertical front sight is visually placed in the field of view seen in the notched area of the sight so that the top of the front sight is even with the top of the notch sight. The target is visually positioned either partially behind or on top of the front sight. To aim straight ahead, the front sight is visually placed in the center of the field of view seen through the notched portion of the sight. To adjust the aim of the firearm for changing distance to the target, for windage, or movement of the target, for example, the firearm is moved in a direction appropriate to visually maintain the front sight within the field of view of the notch while keeping the target in close visual proximity to the top of the front sight.
The small field of view provided a shooter by a notch sight permits only minor adjustments in the aim of the firearm before the front sight becomes obscured by the bulk material adjacent to the notched portion of the sight. This limitation can cause several problems for the shooter. One problem is a difficulty in quickly acquiring a target when sighting through the notched portion of the sight. Another problem is the tendency of a shooter to lose sight of a moving target when viewing through the notched portion of the sight as the shooter leads the moving target. One of the most significant problems facing a shooter with a notch sight is an increased danger of failing to see an unintended target in an area in which the shooter is aiming.
Another limitation of notch sights is a dependence of the sights on lighting conditions. For example, in low light conditions it is often difficult to see a vertical front sight to visually align it with the notched portion of the rear notch sight. In angled light, such as from a street light or from sunlight at dusk or dawn, optical illusions can occur that cause the shooter's eye to misperceive the precise position of the front sight relative to the notch or to misperceive the position of the target itself. The limited field of view provided by the rear notch sight compounds the difficulty in seeing such a visually altered front sight.
Aperture sights provide a shooter with a wider field of view through the sight than notch sights. Despite a greater field of view through aperture sights, aiming refinements are usually more difficult with aperture sights than with notch sights. A conventional aperture sight is a circular ring or tube mounted atop a firearm barrel near the rear end of the barrel.
One of the initial uses of aperture sights was to hunt dangerous game. An aperture sight is particularly suited for this task by providing an unobstructed opening through which a shooter can easily survey terrain for stationary or moving targets while viewing through the sight. Once a target is identified, the aperture sight enables the shooter to continue to view the target through the sight and grossly adjust the aim of the firearm at the target. Since the aperture does not obscure a target at close range and because the size and proximity of the target usually does not require a high degree of aiming refinement, the aperture sight is particularly suited for facing charging game.
In many uses, the circular rear aperture sight is visually aligned with another circular aperture sight positioned atop the barrel toward the front, or open, end of the barrel. When a user looks through both sights together, the visual impression is one in which the rear aperture sight appears larger than the front aperture sight. In general, as the firearm is aimed directly at a target at medium range, the target appears to be located in the center of the front aperture sight with the front aperture sight in turn appearing to fit concentrically within the rear aperture sight.
One attempt to provide a means to align a front aperture sight with a rear aperture sight is disclosed in U.S. Pat. No. 4,745,698, issued to Schwulst. In this disclosure, the front sight has light emitting diodes, or other low light source, placed around the circumference of the aperture portion of the front sight. The light source faces toward the rear of the firearm and into the shooter's eye. In order to aim at a target directly in front of the firearm, the ring of luminous dots formed by the light emitting diodes on the front aperture sight is visually positioned within and partially obscured by the circumference of the aperture portion of the rear aperture sight. Once these apertures are aligned with respect to one another, the shooter visually positions a target in the center of the apertures to aim a firearm at the target.
The Schwulst sights and other aperture sights highlight the central problem with conventional aperture sights, namely the inability of these sights to readily provide the shooter with means to make rapid and accurate visual aiming adjustments to targets that are not positioned visually in the center of the aperture portion of the sight. This limitation is particularly evident if the shooter is required to compensate for changing distance to the target, windage, or motion of the target that visually places the target away from the center area of the aperture.
Accurate aiming of a firearm with some conventional circular aperture sights has been improved somewhat when the sight is used with a conventional vertical front sight. In use, the top of the vertical front sight assists the shooter in visually locating the central region of the aperture portion of the sight. The front sight is then used to visually place the target on top of the front sight in the central region of the aperture portion of the sight. Even with the aid of a vertical front sight, a circular aperture sight does not provide a shooter with visual reference points that permit rapid and precise aiming refinements at a target, particularly when the target is visually positioned away from the central portion of the aperture.
A rear aperture sighting device having visual reference points in the form of straight edges, angles, and vertices framing the aperture portion of the sighting device would provide a user with means to more effectively utilize a vertical front sight to perform rapid and accurate target acquisition and aiming refinements, particularly with targets that are not visually positioned in the center of the aperture.